Altered chromatin landscape in circulating T follicular helper and regulatory cells following grass pollen subcutaneous and sublingual immunotherapy.

ABSTRACT

BACKGROUND: Allergen-specific immunotherapy is a disease-modifying treatment that induces long-term T-cell tolerance. OBJECTIVE: We sought to evaluate the role of circulating CXCR5+PD-1+ T follicular helper (cTFH) and T follicular regulatory (TFR) cells following grass pollen subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT) and the accompanying changes in their chromatin landscape. METHODS: Phenotype and function of cTFH cells were initially evaluated in the grass pollen-allergic (GPA) group (n = 28) and nonatopic healthy controls (NAC, n = 13) by mathematical algorithms developed to manage high-dimensional data and cell culture, respectively. cTFH and TFR cells were further enumerated in NAC (n = 12), GPA (n = 14), SCIT- (n = 10), and SLIT- (n = 8) treated groups. Chromatin accessibility in cTFH and TFR cells was assessed by assay for transposase-accessible chromatin sequencing (ATAC-seq) to investigate epigenetic mechanisms underlying the differences between NAC, GPA, SCIT, and SLIT groups. RESULTS: cTFH cells were shown to be distinct from TH2- and TH2A-cell subsets, capable of secreting IL-4 and IL-21. Both cytokines synergistically promoted B-cell class switching to IgE and plasma cell differentiation. Grass pollen allergen induced cTFH-cell proliferation in the GPA group but not in the NAC group (P < .05). cTFH cells were higher in the GPA group compared with the NAC group and were lower in the SCIT and SLIT groups (P < .01). Time-dependent induction of IL-4, IL-21, and IL-6 was observed in nasal mucosa following intranasal allergen challenge in the GPA group but not in SCIT and SLIT groups. TFR and IL-10+ cTFH cells were induced in SCIT and SLIT groups (all, P < .01). ATAC-seq analyses revealed differentially accessible chromatin regions in all groups. CONCLUSIONS: For the first time, we showed dysregulation of cTFH cells in the GPA group compared to NAC, SCIT, and SLIT groups and induction of TFR and IL-10+ cTFH cells following SCIT and SLIT. Changes in the chromatin landscape were observed following allergen-specific immunotherapy in cTFH and TFR cells.